                 actx-position (+ 0.5 (get positions actx-id))
                 wait-chs (:wait-chs actx-info)
                 chs (:chs vis)
-                line-height 21]
+                line-height 21
+                stroke-width 1]
             (map (fn [kv]
                    (let [[ch wait-kind] kv
                          ch-info (get chs ch)

      (let [[actx event] (<! event-ch)
            [verb step & args] event
            vis-event-handler (get (get vis-event-handlers verb) step)
            positions (atom {})]
        (vis-event-handler vis actx args)
        (let [actx-ch-ch-infos (group-by #(:first-taker-actx (second %)) (:chs @vis))]
          (set-el-innerHTML "vis-html"
                            (apply str (flatten (vis-html-actx @vis @root-actx positions
                                                               actx-ch-ch-infos))))
          (set-el-innerHTML "vis-svg"
                            (apply str (flatten (vis-svg-actxs @vis @positions))))
          (set-el-innerHTML "event"
                            (str num-events ": " (last actx) " " verb " " step " " args))))
      (recur (inc num-events)))
    (ago w-actx w
         (reset! root-actx w-actx)
         (let [in (achan-buf w-actx 100)

       [])
     "</div>"]))

(defn vis-svg-actxs [vis positions delta]
  ["<defs>"
   "<marker id='triangle'"
   " viewBox='0 0 10 10' refX='0' refY='5'"
